In fiber optic networks, optical active devices are key components. It can convert electrical signals and optical signals to each other, the optical transmission system of the heart. Optical active devices are divided into the following three categories.
A. Light Source
The device that converts electrical signal into optical signal is called light source. The main light sources are light emitting diodes (LED) and laser diodes (LD).
B. Optical Detector
The device that converts optical signal into electrical signal is called optical detector. The main optical detectors are photodiode and avalanche photodiode.
The optical signal transmitted through the optical fiber reaches the receiving end, the receiving end has a light receiving element signal. But since we know of light has not yet reached the level of awareness of the electricity, so we can not direct the optical signal obtained by reducing the original signal. Between them, there are still one of the optical signals into electrical signals, and then by the electronic circuit to amplify the process, and finally restore the original signal. The reception switching element is called the light detector, or photodetector, short detector, also known as photo-detector or a photodiode. Common optical detector comprising PN photodiodes, PIN photodiodes and avalanche photodiodes (APD). Optical fiber communication systems require optical detector to be high sensitivity, fast response, low noise, stable and reliable.
C. Optical Amplifier
Optical fiber amplifier has become active devices rookie. Erbium-doped fiber amplifier (EDFA) has currently a large number of applications , while optical fiber Raman amplifier (FRA) is very promising.
Fiber amplifiers can not only amplify the optical signal directly, but also have real-time, high gain, broadband, online, low-noise, low-loss optical zoom function. They are essential key components in the new generation of fiber optic communication systems.
Since this technology not only solved the attenuation of optical network transmission speed and distance limitations, more importantly, it created a 1550nm band WDM, which can enable ultra high-speed, large-capacity, ultra-long haul wavelength division multiplexing (WDM), Dense Wavelength Division Multiplexing (DWDM), optical transmission, optical soliton transmission becomes a reality. It is epoch-making milestone in the history of optical fiber optic communication development.
In practical optical fiber amplifiers, there are mainly EDFA, semiconductor optical amplifier (SOA) and FRA, of which the EDFA amplifier with its superior performance is now widely used in long-distance , large capacity, high-speed optical fiber communication systems, access networks, optical fiber CATV networks, military systems in areas such as power amplifiers, repeater amplifiers and preamplifiers. Optical Fiber Amplifier is generally constituted of the gain medium optical fiber amplifier, the pump light input-output coupling structure.
The fiber optic amplifier plays a significant and key role within the enhancing the capacity for a communication system to deliver information. The light signals can be transmitted by the use of optical transmitters, optical receivers and optical fiber.
The optical amplifier is a device amplifying an optical signal directly, without the need to first convert it to an electrical signal. The most popular parameter of gain from it is bandwidth and noise performance. It’s compensation for the wakening of knowledge throughout the transmission, due to fiber optic attenuation. The wavelength and also the power of the input fiber signal are decided through the fans.
Fiber optic amplifier has industry’s highest color resolution and simple amplifier, and sensor setup will lead to enhanced stability for previously difficult detection applications. What is more, it can offer you very high-output powers with diffraction-limited beam quality when utilizing it. Its saturation characteristics have the ability to prevent any intersymbol interference so that it is vital for optical fiber communications. That fiber amplifiers are often operated in the strongly saturated regime enables the highest output power. The amplified spontaneous emission will affect its gain achievable. It’s important to safeguard a high-gain amplifier from the parasitic reflections, for the parasitic laser oscillation or perhaps to fiber will be damaged by these.
Optical amplifiers could be transferred in the forward direction, in the backward direction, or bidirectional. However, its direction from the pump wave won’t modify the small-signal gain, the ability efficiency of the saturated amplifier as well as the noise characteristics. Furthermore, the amplification of a weak signal-impulse in a monocentrics nonlinear medium could be allowed because of it. Along with the advancement of we’ve got the technology, the caliber of it’s been improved greatly that it is well-liked by many companies. Besides, there are all sorts of products on the market so the people might have more opportunities to pick one that’s ideal for their needs.
However, when it comes to choice for the fiber optic amplifier, the best solution is to figure out the best providers that focus on this type of products. Because the components of this kind of products are complex, and you’re simply unfamiliar with the related details about it. The professional providers can use their professional knowledge and lots of years of experiences to provide you with wise advice, which can help you make a right decision. Of course, some providers provides you with certain warranty so that you can take it to their company for repair when it reduces.
CATV EDFA is a type of fiber optic amplifier. It is used to increase the output power of the transmitter and prolong the signal transmission distance. It’s widely requested TV signals, video, telephone, and data long haul transmission. FiberStore provides high output power and low noise EDFA CATV Amplifiers with selection of output power from 14dBm to 27dBm to meet the requirements of a high-density solution for the large-scale distribution of broadband CATV video and knowledge signals to video overlay receivers in a FTTH/FTTP or PON system.
Optical amplifier is an optical communication system device. It amplifies an optical signal directly, without converting an optical signal into an electrical signal.
Erbium-doped fiber amplifier (EDFA) is the first successful optical amplifier invented by the UK Southampton University and JP Tohoku University. It is one of the greatest invention in optical communication. Erbium-doped optical fiber is incorporated a small amount of a rare earth element erbium (Er) ion. It is the core of the EDFA. From the late 1980s, the EDFA research has been making a major breakthrough continuously. As WDM technology greatly increases the capacity of optical communication, it becomes the most widely used optical amplifier device in the optical fiber communication.
EDFA is constituted by a period of erbium-doped fiber (about 10-30m) and pump light source. The stimulated emission of erbium-doped fiber under the action of the pump light source (wavelength 980nm or 1480nm), and the radiation of light varies with the change of the input optical signal, which is equivalent to the input optical signal the amplification. Studies have shown that the erbium-doped fiber amplifiers are typically 15-40dB of gain can be obtained, and the distance relay can be increased on the basis of the original more than 100km. So, why did scientists use erbium-doped fiber element to increase the intensity of light? We know that erbium is a kind of rare earth elements, and rare earth elements has its special structural features. Over the years, people have been using the method which doped rare earth elements in optical devices to improve the performance of optics, so this is not an accidental factor. In addition, why is the pump source wavelength chosen from 980nm or 1480nm? In fact, the pumping light source wavelength could be 520 nm, 650nm, 980nm and 1480nm. But the practice has proved that the 1480nm wavelength pumping light source laser efficiency is the highest, followed by the 980nm wavelength.
The main advantage of EDFA is a high gain, wide bandwidth, high output power, high pumping efficiency, low insertion loss, and not sensitive to the polarization state.
1. Its amplifying area happens to coincide with the minimum loss area of single-mode fiber. This reduces the transmission loss of the light signal which can be transmitted relatively far distance.
2. It is transparent to digital signal format and data rate.
3. Its amplification bandwidth is so wide that dozens or even hundreds of channels can be transmitted in the same fiber.
4. It has low noise figure close to the quantum limit, which means that multiple amplifiers can be cascaded.
5. Its gain saturation recovery time is long, and has a very small crosstalk between the respective channels.
When EDFA is used in conventional optical digital communication system applications, we can save a lot of optical repeaters, and the distance relay could also be increased significantly, which is of great significance for the long-haul fiber optic cable trunking systems.
The main applications include:
1. It can be used as the light distance amplifier. Traditional electronic fiber optic repeater has many limitations. Such as a digital signal and the analog signal conversion, the repeater should be changed accordingly; repeater changes after the device is changed from a low rate to a high rate; only transmit the same wavelength of the optical signal, and the complex structure, expensive, and so on. Erbium-doped fiber amplifier to overcome these shortcomings, not only do not have to change with the change in the way of the signal, and equipment expansion or for optical wavelength division multiplexing, no need to replace.
2. It can be used for the transmitter amplifier and the optical receiver preamplifier. For the rear of the optical transmitter amplifier, the transmit power of the laser is increased from 0dB to +10 db. Optical receiver preamplifier, the sensitivity can also be greatly improved. Therefore, only the line of 1-2 erbium-doped amplifier, the signal transmission distance can be increased to 100-200km. In addition, the erbium-doped fiber amplifier problem to be solved the unique advantages of the erbium-doped fiber amplifier has been recognized by the world, and to be more widely used. However, the erbium-doped fiber amplifier there are also some limitations. For example, in the long-distance communication can not drop channel, each station business contacts is more difficult, not easy to find fault, pumping light source life is not long, as the optical fiber communication technology continues to progress, these problems will be satisfactorily resolved.